1. Field of the Invention
The present invention generally relates to a climate control system. More specifically, the present invention relates to an automatic climate control system for an automotive vehicle passenger compartment, which utilizes measured sun load and/or virtual sun load depending on daylight conditions in controlling the system in order to optimize performance of the climate control system.
2. Background Information
For many years, automotive vehicles have been provided with climate control systems in order to provide a more comfortable environment for the driver and any passengers. In recent years, climate control systems have been provided that automatically adjust to maintain a desired cabin temperature of the driver and/or passengers.
One type of vehicle automatic climate control system uses ambient temperature sensors and sun load sensors to obtain information on exterior air temperature and solar energy load. The information gathered from the sensors is used in a logic control system to establish airflow data and outlet temperature for the temperature control system in the vehicle passenger compartment. The outside ambient air temperature sensor must be strategically placed so that it is positioned away from heat sources such as the engine of the vehicle. A common location for the ambient temperature sensor is behind the forward radiator grille. This provides fair performance at high vehicle speeds but relatively poorer performance at lower vehicle speeds and/or if the vehicle is traveling in the same direction as surface winds. The sun load sensor(s) are typically located in the upper vehicle dash surface. In this location the sun load sensor(s) may be subjected to shadows (shade), which can cause readings that are inconsistent with the actual solar energy load on the vehicle passenger compartment. Also, when so positioned, the sun load sensor(s) have poor directional sensitivity, i.e., the sensitivity of the sun load sensor(s) vary depending upon the sun angle, which varies seasonally as well as hourly.
U.S. Pat. No. 5,832,990 discloses a climate control system that takes into account airflow, as well as interior temperature, outlet temperature of the system and general comfort parameters while managing the total heat flux. This system uses thermodynamic interaction of the comfort parameters, the interior temperature, the outlet temperature and airflow, as well as other control variables, in accordance with a control logic to improve climate control. However, as in the case of the prior temperature control system, the control system of the '990 patent requires a sun load sensor and an ambient temperature sensor. Thus, this system suffers from some of the same deficiencies as the prior system.
U.S. Pat. No. 5,995,889 discloses a temperature control system that eliminates the need for an external ambient temperature sensor and sun load sensor(s) in order to overcome some of the problems with the prior systems using such sensors. This system regulates outlet temperature and blower speed automatically using a processor with stored control algorithms that rely upon data including virtual ambient temperature and virtual sun load heat flux. In certain driving situations such as when sun load sensors would be shaded, this system performs better than the prior systems utilizing sensors. However, it suffers from other deficiencies. In particular, in certain driving conditions such as when sun load sensors would be in direct sunlight (i.e. when direct sun load impingement on the passenger(s) is present), this system does not work as well as the prior systems utilizing sensors.
In view of the above, it will be apparent to those skilled in the art from this disclosure that there exists a need for an improved automatic climate control system for a vehicle. This invention addresses this need in the art as well as other needs, which will become apparent to those skilled in the art from this disclosure.